Because of their low power consumption, high luminance and high durability, light emitting diodes (LEDs) are in the spotlight as a light source for an illumination apparatus with which incandescent lamps, fluorescent lamps and the like are replaced. However, since a single LED provides less light intensity than a fluorescent lamp, a light emitting device including a plurality of LEDs is used for a general illumination apparatus having LEDs as a light source.
As one example of such a type of light emitting device, as shown in FIG. 19A, there has been known a light emitting device 101 in which a plurality of LEDs 102 is mounted on an elongated board 103 in a line and a semicylindrial transparent resin part 104 is provided to cover the LEDs 102 (see, e.g., Japanese Patent Application Publication No. 2002-299697 (JP2002-299697A).
In addition, as shown in FIG. 20A, there has been proposed an illumination apparatus 110 in which a plurality of LED packages 101 having respective hemispherical transparent resin parts is arranged and a diffusion and transmission panel 107 is disposed adjacent to the front side of the LED packages 101.
However, in the light emitting device 101 disclosed in JP2002-299697A, lights emitted from the LEDs 102 are propagated straight through or refracted in the directly upward direction of the LEDs 102 by the semicylindrical transparent resin part 104 to be collected. On that account, a distribution of emitted lights shows a high directivity in a light output direction, as shown in FIG. 19B. Accordingly, in an illumination apparatus including such a light emitting device, luminance of portions immediately above the LEDs 102 becomes increased, and, even if a light diffusion cover or the like is provided to cover the LEDs 102, a luminance distribution at the light output surface becomes non-uniform, and surface reflection is likely to occur.
In addition, in the above-mentioned illumination apparatus 110, luminance of portions immediately above the LED packages 101 of the diffusion and transmission panel 107 becomes increased. This results in a non-uniform distribution of luminance at the output surface (the diffusion and transmission panel 107) of the illumination apparatus, thereby resulting in a granule-like distribution of the lights, and causing surface reflection, as shown in FIG. 20B.